Discarded cigarette butts provide energy storage solution

Used-cigarette butts have been converted into a material that could be used in supercapacitors for energy storage.

It is estimated that as many as 5.6 trillion used-cigarettes are deposited into the environment worldwide every year, but a group of scientists from South Korea may have found a use for this litter.

Using a simple, one-step burning technique called pyrolysis the team transformed the cellulose acetate fibres of cigarette filters into a carbon-based material with superior performance to commercially available carbon, graphene and carbon nanotubes commonly used in supercapacitors – electrochemical devices used to store energy that are distinct from batteries.

It is hoped the material can be used to coat the electrodes in such devices, whilst also offering a solution to the growing environmental problem caused by used-cigarette filters.

“Our study has shown that used-cigarette filters can be transformed into a high-performing carbon-based material using a simple one step process, which simultaneously offers a green solution to meeting the energy demands of society,” said co-author of the study Professor Jongheop Yi, from Seoul National University.

“Numerous countries are developing strict regulations to avoid the trillions of toxic and non-biodegradable used-cigarette filters that are disposed of into the environment each year—our method is just one way of achieving this.”

Supercapacitors are generally made of highly porous carbon impregnated with a liquid electrolyte and are long-lasting and quick to recharge, but their low-energy density means they must be re-charged frequently.

In a paper published in journal Nanotechnology, the researchers have demonstrated that the burning process results in a carbon-based material that contains a number of tiny pores, increasing its performance as a supercapacitive material.

“A high-performing supercapacitor material should have a large surface area, which can be achieved by incorporating a large number of small pores into the material,” said Professor Yi.

“A combination of different pore sizes ensures that the material has high power densities, which is an essential property in a supercapacitor for the fast charging and discharging.”

Once fabricated, the carbon-based material was attached to an electrode and tested in a three-electrode system to see how well the material could adsorb electrolyte ions (charge) and then release electrolyte ions (discharge).

The material stored a higher amount of electrical energy than commercially available carbon and also had a higher amount of storage compared to graphene and carbon nanotubes, as reported in previous studies.